Here are Floyd Mayweather's potential opponents for his last fight ever

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After winning a unanimous decision in his historic bout against Manny Pacquiao in May, Floyd Mayweather (48-0, 26 knockouts) has yet to name who his opponent will be for his final fight in September. Several names have been mentioned and there have been plenty of rumors, but with just a few months before the expected fight no one knows who will get the last opportunity to try to take down the undefeated Mayweather before he retires.

Here are six of his potential opponents ranked in order by likelihood:

The Favorites

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1. Andre Berto (30-3, 23 knockouts): Berto is one of two names Mayweather mentioned as his preferred potential opponent. While some thought he was joking, Mayweather reiterated the fact he was "100% serious" in an interview with Fight Hype's Ben Thompson. While Berto may not be the most deserving, he could still pose serious problems to Mayweather. Berto's a two-time welterweight champion who — as his former trainer Tony Morgan said — has "natural speed" and "natural power." While all three of his losses have come within his past six fights, Berto has won his last two bouts by way of unanimous decision and technical knockout respectively. Berto gets the slight nod over the number two fighter on this list based purely on his record and quality of past opponents.

2. Karim Mayfield (19-2, 11 knockouts): The second of the two fighters Mayweather named as the favorite to have a chance at him in September, Mayfield is relatively unknown compared to Berto. While Berto is a former welterweight champion and has fought big-name fighters — such as Freddy Hernandez, Victor Ortiz, and Robert Guerrero — Mayfield has yet to face the same level of competition. However, he has sparred some of the top fighters in the world as many high-level boxers like to use Mayfield as one of their frequent sparring partners. In fact, Mayfield told GMA News' JM Siasat he "whooped [Manny] Pacquiao and [Amir] Khan" in past sparring sessions and would "give Floyd his first loss in a highly explosive fight."

Still Possible

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3. Amir Khan (31-3, 19 knockouts): Khan, another former Pacquiao sparring partner, has been a frequent name mentioned as a possible opponent for Mayweather throughout the years. And after a unanimous decision over Chris Algieri in May he seemed poised to finally get his chance at the undefeated boxing king. In early June, Khan even went as far as saying "the fight could be confirmed within the next two weeks." Yet, Mayweather reportedly responded "no" when asked if he was planning on fighting Khan in September. Known for his speed and having "some of the fastest hands in boxing," Khan would arguably give Mayweather the most trouble out of all of his potential opponents. He's won his last five fights by four unanimous decisions and one referee technical decision.

Unlikely

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4. Shawn Porter (26-1-1, 16 knockouts): Porter recently dominated Mayweather's prodigy, and "little brother," Adrian Broner in a lopsided unanimous decision win (one judge had it as 118-108 for Porter), and called out Mayweather in the process, so it's possible Mayweather may want a little payback. It wouldn't be the first time such a scenario took place, Mayweather fought Marcus Maidana after the Argentinian fighter won a unanimous decision over Broner — and, with unanimous decision wins over Broner, Devon Alexander, and Julio Diaz, most would agree that Porter is in the same class as Maidana. Mayweather has said he wants Porter to fight in the same ring as him in September, but, not as his opponent, as an undercard in a rematch against Broner.

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5. Timothy Bradley (31-1-1): While Bradley is the most-recognized name on this list, he's ranked third on ESPN's welterweight division rankings (behind only Mayweather and Pacquiao), he's also one the least-likely opponents. Bradley shares the same promoter as Pacquiao, Top Rank's Bob Arum. Mayweather and Arum have publicly feuded ever since Mayweather left Top Rank in 2006. The two despised each other so much it took them five years to finally come to terms for the historic Mayweather-Pacquiao showdown. Thus, it's very unlikely they'll be able to work out a contract for Bradley to fight Mayweather in just a few months.

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6. Kell Brook (35-0, 24 knockouts): A week ago, Brook - the IBF welterweight title-holder - would have been placed into the "Still Possible" category, but his entire pitch for a bout against Mayweather went up in smokes when the WBO stripped Mayweather of his title and named Timothy Bradley the new champion. Brook's promoter Eddie Hearn had been hyping up the potential fight as a chance for Mayweather - who at the time was the WBO, WBC, and WBA title-holder - to unify the four welterweight belts. But, with Mayweather no longer considered the WBO welterweight champion, that's no longer possible. It appears that Brook has accepted the fact Mayweather won't face him, and it's now believed he'll fight Brandon Rios instead.